feat: infer base from package json scripts during migration (#993)

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## PR Checklist

- [x] Addresses an existing open issue: fixes #933
- [x] That issue was marked as [`status: accepting
prs`](https://github.com/JoshuaKGoldberg/create-typescript-app/issues?q=is%3Aopen+is%3Aissue+label%3A%22status%3A+accepting+prs%22)
- [x] Steps in
[CONTRIBUTING.md](https://github.com/JoshuaKGoldberg/create-typescript-app/blob/main/.github/CONTRIBUTING.md)
were taken

## Overview

Add a naive solution for checking the existing `package.json` during
migration to infer the base.

🐸

---------

Co-authored-by: Josh Goldberg <git@joshuakgoldberg.com>

src/shared/options/getBase.test.ts

@@ -0,0 +1,57 @@
+import { describe, expect, it, vi } from "vitest";
+
+import { getBase } from "./getBase.js";
+
+const mockReadPackageData = vi.fn();
+vi.mock("../packages.js", () => ({
+	get readPackageData() {
+		return mockReadPackageData;
+	},
+}));
+
+describe("getBase", () => {
+	it("should return minimum with minimum scripts", async () => {
+		mockReadPackageData.mockImplementationOnce(() =>
+			Promise.resolve({
+				scripts: {
+					build: "build",
+					lint: "lint",
+					test: "test",
+				},
+			}),
+		);
+
+		expect(await getBase()).toBe("minimum");
+	});
+	it("should return common with common scripts", async () => {
+		mockReadPackageData.mockImplementationOnce(() =>
+			Promise.resolve({
+				scripts: {
+					build: "build",
+					lint: "lint",
+					"lint:knip": "knip",
+					test: "test",
+				},
+			}),
+		);
+
+		expect(await getBase()).toBe("common");
+	});
+	it("should return everything with everything scripts", async () => {
+		mockReadPackageData.mockImplementationOnce(() =>
+			Promise.resolve({
+				scripts: {
+					build: "build",
+					lint: "lint",
+					"lint:knip": "knip",
+					"lint:md": "md",
+					"lint:package-json": "package-json",
+					"lint:packages": "packages",
+					test: "test",
+				},
+			}),
+		);
+
+		expect(await getBase()).toBe("everything");
+	});
+});

src/shared/options/getBase.ts

@@ -0,0 +1,34 @@
+import { readPackageData } from "../packages.js";
+import { OptionsBase } from "../types.js";
+
+const commonScripts = new Set(["lint:knip", "should-semantic-release", "test"]);
+
+const everythingScripts = new Set([
+	"lint:md",
+	"lint:package-json",
+	"lint:packages",
+	"lint:spelling",
+]);
+export async function getBase(): Promise<OptionsBase> {
+	const scripts = Object.keys((await readPackageData()).scripts ?? {});
+
+	if (
+		scripts.reduce(
+			(acc, curr) => (everythingScripts.has(curr) ? acc + 1 : acc),
+			0,
+		) >= 3
+	) {
+		return "everything";
+	}
+
+	if (
+		scripts.reduce(
+			(acc, curr) => (commonScripts.has(curr) ? acc + 1 : acc),
+			0,
+		) >= 2
+	) {
+		return "common";
+	}
+
+	return "minimum";
+}

src/shared/options/readOptions.test.ts

@@ -111,6 +111,13 @@ vi.mock("./createOptionDefaults/index.js", () => ({
 	},
 }));
 
+const mockReadPackageData = vi.fn();
+vi.mock("../packages.js", () => ({
+	get readPackageData() {
+		return mockReadPackageData;
+	},
+}));
+
 describe("readOptions", () => {
 	it("returns a cancellation when an arg is invalid", async () => {
 		const validationResult = z
@@ -524,4 +531,40 @@ describe("readOptions", () => {
 			},
 		});
 	});
+
+	it("infers base from package scripts during migration", async () => {
+		mockReadPackageData.mockImplementationOnce(() =>
+			Promise.resolve({
+				scripts: {
+					build: "build",
+					lint: "lint",
+					test: "test",
+				},
+			}),
+		);
+		expect(await readOptions(["--offline"], "migrate")).toStrictEqual({
+			cancelled: false,
+			github: mockOptions.github,
+			options: {
+				...emptyOptions,
+				...mockOptions,
+				access: "public",
+				base: "minimum",
+				description: "mock",
+				directory: "mock",
+				email: {
+					github: "mock",
+					npm: "mock",
+				},
+				guide: undefined,
+				logo: undefined,
+				mode: "migrate",
+				offline: true,
+				owner: "mock",
+				skipAllContributorsApi: true,
+				skipGitHubApi: true,
+				title: "mock",
+			},
+		});
+	});
 });

src/shared/options/readOptions.ts

@@ -10,6 +10,7 @@ import { augmentOptionsWithExcludes } from "./augmentOptionsWithExcludes.js";
 import { createOptionDefaults } from "./createOptionDefaults/index.js";
 import { detectEmailRedundancy } from "./detectEmailRedundancy.js";
 import { ensureRepositoryExists } from "./ensureRepositoryExists.js";
+import { getBase } from "./getBase.js";
 import { GitHub, getGitHub } from "./getGitHub.js";
 import { getPrefillOrPromptedOption } from "./getPrefillOrPromptedOption.js";
 import { optionsSchema } from "./optionsSchema.js";
@@ -44,6 +45,10 @@ export async function readOptions(
 		tokens: true,
 	});
 
+	if (mode === "migrate" && !values.base) {
+		values.base = await getBase();
+	}
+
 	const mappedOptions = {
 		access: values.access,
 		author: values.author,

src/shared/types.ts

@@ -19,6 +19,7 @@ export interface PartialPackageData {
 	email?: string;
 	name?: string;
 	repository?: { type: string; url: string } | string;
+	scripts?: Record<string, string>;
 }
 
 export type OptionsAccess = "public" | "restricted";